function test(ctx) {
    //drawLine(ctx, 100, 100, 400, 400, '#0f0', 5);
    //ctx.fillRect(200, 200, 20, 200);
    //ctx.strokeRect(10, 10, 50, 50);
    //ctx.clearRect(210, 210, 5, 100);
    
    ctx.arc(250, 250, 200, 0, Math.PI*0.5, true);
    ctx.stroke();
    ctx.fillText('abc', 10, 10, 200);
    function drawLine(ctx, x1, y1, x2, y2, color, width) {
        ctx.beginPath();
        ctx.moveTo(x1, y1);
        ctx.lineTo(x2, y2);
        ctx.strokeStyle = color;
        ctx.lineWidth = width;
        ctx.stroke();
        ctx.closePath();
    }
}